In the past few weeks I’ve been asked several questions about the northern lights, also called the aurora borealis. In this month’s column I will answer some of these questions and introduce you to this mysterious and unpredictable display of light in the night sky.

All objects in the sky appear to rise in the east and set in the west. The stars are not really moving; it is the rotation of the Earth from west to east that causes this apparent clockwise motion. The speed of this rotation is so constant that it can be used to keep time.